Choice of flowers by foraging honey bees ( Apis mellifera ): possible morphological cues

Honey bees foraging for nectar on lavender ( Lavandula stoechas ) chose inflorescences with more of their flowers open. The number of open flowers predicted whether an inflorescence was visited by bees, inspected but rejected, or ignored. Inflorescences chosen arbitrarily by observers had numbers of open flowers intermediate between those of visited and ignored inflorescences. Differences in morphological characters between types of inflorescence correlated with nectar volume and sugar weight per flower so that visited inflorescences had a disproportionately greater volume of nectar and weight of sugar per flower and greater variance in nectar volume. Although there were significant associations between nectar content and the morphological characters of inflorescences, discriminant function analysis revealed discrimination on the basis of morphology rather than nectar content. Visited inflorescences tended to have smaller than average flowers but bees tended to probe the largest flowers on visited inflorescences. Choice of flowers within inflorescences is explicable in terms of the relationship between flower size and nectar content.